U.S. Pat. No. 6,241,709 discloses an injection device, in which a holder, which carries an injection needle and in which a carpule containing injection fluid is arranged, is moved relative to the housing. By retraction of the holder, the injection needle is concealed in the housing before the injection operation. This reduces the user's anxiety about the needle.
In order to make the injection device, it is known from U.S. Pat. No. 6,241,709 to arrange the holder for the carpule containing injection fluid on the driving device in such a manner that the plunger, which serves to inject injection fluid from the container, bears against the stopper of the carpule before the first injection. A micro-grid structure is provided in U.S. Pat. No. 6,241,709 in order to fix the holder.
The production process causes the position of the stopper in the carpule to be subject to comparatively high tolerances. A different position of the injection needle in the housing therefore arises depending on the position of the stopper. Since the distance which the container covers in relation to the housing is structurally predetermined, the insertion depth changes in dependence on the position of the injection needle. In order to control the insertion depth, a sleeve with which the insertion depth can be changed manually by the operator is known from U.S. Pat. No. 6,241,709.
For certain applications, it is advantageous to carry out the injection with a precisely defined insertion depth. This is expedient in particular if the injection is carried out with a very short injection needle. In the case of very short injection needles, it firstly has to be ensured that a sufficient insertion depth is reached so that the injection fluid is securely injected. Secondly, it has to be ensured that the needle holder does not emerge too far out of the housing.